1. Field of the Invention
The present invention relates generally to medical devices and, more particularly, to hemostasis valves for use within percutaneous catheter introducers.
2. Description of the Prior Art
The use of catheter introducers in percutaneous medical procedures is well known in the art. A catheter introducer typically includes a long sheath having a first end positioned within a vein or artery of a patient and a second end positioned immediately external to the epidermis of the patient. Since the control of bleeding is obviously essential when such catheter introducers are utilized, conventional catheter introducers include a hemostasis valve assembly positioned at the second end of the sheath to permit a loader, catheter or other medical instrument to be introduced into the body of the patient through the sheath while precluding blood from flowing out of the introducer.
In many percutaneous medical procedures, a small diameter guide wire is passed through the sheath of the introducer and inserted into a vein or artery. The guide wire serves as a guide for a large diameter loader, catheter or other medical instrument employed later in the procedure. It is therefore necessary for the valve assembly to provide a sufficient seal around the small diameter guide wire to prevent excessive blood loss through the introducer. However, the valve assembly must also allow passage of, and sealingly engage, the large diameter loader, catheter, or other medical instrument, so as to prevent the flow of blood through the introducer.
One type of valve commonly used to control the flow of blood is referred to as a "duckbill" valve. A conventional duckbill valve includes a pair of walls, each having a generally planar configuration, which converge and intersect along a line or slit. However, such duckbill valves are not well suited for use alone in catheter introducers where medical instruments are to be inserted through the valve. When an instrument is inserted into a conventional duckbill valve, it passes between the converging walls of the valve and through the slit. This causes the walls to separate and to create an undesirable flow channel between the slit and the instrument.
U.S. Pat. No. 4,929,235 discloses a catheter introducer valve assembly designed to overcome the limitations of the prior art duckbill valves. The valve assembly includes a first valve having a Y-shaped slit which seals off any flow of blood from the sheath of the introducer during the time a catheter tube is not present. A second valve, typically a disc seal with a small through-hole, seals around the catheter tube during and after the insertion of the catheter tube into the introducer so as to seal off any flow of blood.
The prior art catheter introducer valve assemblies have been successful in accomplishing the primary purpose of shutting off the flow of blood in the sheath when no medical instrument is present therein. Further, the prior art valve assemblies have been effective in allowing passage of and sealingly engaging the outer diameter of a catheter or other medical instrument.
However, the prior art catheter introducer valve assemblies have been unable to provide adequate seals around both a small diameter guide wire and large diameter medical instrument passing through the introducer. The prior art valve assemblies typically include a seal which is adapted to sealingly engage around the relatively large diameter medical instrument such that no seal is formed around a relatively small diameter guide wire. With further reference to U.S. Pat. No. 4,929,235, the through-hole of the second valve has a diameter adapted to sealingly engage a catheter or loader having a diameter typically of approximately 0.3 inches. A typical guide wire has a diameter of approximately 0.035 inches such that once the catheter or loader has been removed, leaving the guide wire alone within the valve assembly, a substantial gap exists between the second valve and the guide wire whereby blood may pass through the introducer.
Accordingly, there is a need for a catheter introducer valve assembly which provides for the effective sealing of blood flow during three separate and distinct conditions: when no medical instrument is inserted through the assembly, when a relatively large diameter medical instrument is inserted through the valve assembly, and when a relatively small diameter guide wire is inserted through the valve assembly. In addition, there is a need for a guide wire seal which provides an effective seal around the exterior of a guide wire which alone has been inserted through the valve assembly, but which also provides for the easy passage of a relatively large diameter catheter or loader.